This invention relates generally to chairs and more particularly, to a chair control for tilting chairs.
In the past, mechanisms which controlled the tilting of a tiltable chair have comprised a fixed base, a support post, a fixed frame portion and a moveable frame portion attached to the seat of the chair. The fixed frame portion and the moveable frame portion were pivotally interconnected so that the seat of the chair could be pivoted in a horizontal plane and also be pivoted in a vertical plane. The fixed base contained a support post and was affixed to a set of outwardly extending legs and the upper portion of the support post was screw-threaded which provided a means to adjust the height of the seat of the chair.
The fixed frame portion was affixed to the uppermost part of the support post and a means was provided for interconnecting the fixed frame portion to the moveable frame portion which was attached to the seat of the chair. The moveable frame portion is pivoted about the means and a stopping mechanism was provided to restrict the pivotal movement of the seat.
The means employed in the prior art about which the seat portion and the moveable frame portion pivoted have comprised many different biasing means. Some have included coil springs, flat springs, tension bars and leaf springs. These various devices have proved complicated to manufacture and rather expensive to produce and have not provided a smooth pivot point.
A further disadvantage exhibited by the controls of the prior art is the lack of an efficient and strong stopping means to arrest the movement of the seat of the chair when the chair is tilted backwards and then released to return to the forward position.
The fixed frame portions of the controls of the prior art have shown a tendency to weaken and break after repeated use. This has been found attributable to the constant pressure and pull on the inner plate of the fixed frame portion by the head of the biasing means when the control is in use. This pressure is exerted in the forward and upward directions by the pivoting of the head of the biasing means which tends to pull the inner plate away from the base plate of the fixed frame portion.